This invention has relation to a valve which is utilized in connection with a two-stage, series-parallel fire pump as the transfer valve to achieve either series or parallel operation. More broadly, it relates to a so-called three-way valve having at least three ports open therefrom and in which the internal passageways between the ports can be varied to provide a flow path between one combination of ports and a flow path between a second combination of ports.
The valve of the invention is designed to be substituted for the sleeve or "plug" valve as shown in U.S. Pat. No. 2,900,918 to Thomas et al, granted on Aug. 25, 1959.
This invention also relates to ball type valves wherein the valve body or ball is part-spherical and rotates in a part-spherical cavity in a valve casing. Such a valve is shown in the Thomas et al patent, U.S. Pat. No. 2,800,295, granted in July of 1957.
In U.S. Pat. No. 2,800,295, the water or fluid seal is accomplished by having a sleeve force an O-ring against the outer surface of the part-spherical portion of the valve body or ball. It is typical of ball valves of the prior art that the seals are stationary and the cooperating sealing surfaces are on the ball. In the case of transfer valves this requires two stationary valve seal structures mounted in the valve casing. In contrast, in transfer valves made according to this invention, only one seal structure is required and it moves with the ball while the cooperating sealing surfaces are part of the stationary valve casing.
Typical "three way" ball valves of the prior art divert fluid flow from a common port to either of two other ports through a passageway which causes the fluid to deviate from a linear flow path by 90.degree..
In contrast, in transfer valves made according to the form of the invention as shown, the ports are located at 120.degree. from each other so that the flow path deviates from a linear path by only 60.degree. in either position of the valve.
In transfer valves of the type here involved, there should be no substantial leakage between a valve port which is to be closed during a certain positioning of the valve and the two valve ports which are open to each other through the part-spherical valve body or ball; but often some slight leakage at this point does not seriously affect the operation of a system including the transfer valve.
Conversely, any "leakage" between the two mutually open ports due to clearance between the valve casing and the valve body, for example, is not really "leakage" at all, and in no way inhibits the effectiveness of the valve.
No special search of the prior art has been made, and the two patents cited above, represent the closest prior art presently known to the applicant.